U.S. patent application number 09/984233 was filed with the patent office on 2003-02-27 for method of forming insulation layer in semiconductor devices for controlling the composition and the doping concentration.
Invention is credited to Kang, Jin Yeong, Lim, Jung Wook, Shim, Kyu Hwan, Song, Young Joo.
Application Number | 20030040196 09/984233 |
Document ID | / |
Family ID | 19713584 |
Filed Date | 2003-02-27 |
United States Patent
Application |
20030040196 |
Kind Code |
A1 |
Lim, Jung Wook ; et
al. |
February 27, 2003 |
Method of forming insulation layer in semiconductor devices for
controlling the composition and the doping concentration
Abstract
The present invention relates to a method of forming an
insulating film in a semiconductor device by which the composition
and the doping concentration of oxide are controlled using an
atomic layer deposition method. In case of silicon oxide, a thermal
oxidization process and a deposition process are sequentially
performed to form an oxide film having a good interface
characteristic and the deposition speed. On the other hand, in case
of depositing an oxide film, an oxynitride film and a metal oxide
film, the pulse construction and the supply time of a source and
radical are adjusted to form an optimum oxide film having a good
interface characteristic.
Inventors: |
Lim, Jung Wook; (Daejon-Shi,
KR) ; Song, Young Joo; (Suwon-Shi, KR) ; Shim,
Kyu Hwan; (Daejon-Shi, KR) ; Kang, Jin Yeong;
(Daejon-Shi, KR) |
Correspondence
Address: |
JACOBSON, PRICE, HOLMAN & STERN
PROFESSIONAL LIMITED LIABILITY COMPANY
400 Seventh Street, N.W.
Washington
DC
20004
US
|
Family ID: |
19713584 |
Appl. No.: |
09/984233 |
Filed: |
October 29, 2001 |
Current U.S.
Class: |
438/785 ;
257/E21.268; 257/E21.274; 257/E21.282; 438/786; 438/787;
438/790 |
Current CPC
Class: |
H01L 21/02178 20130101;
H01L 21/3144 20130101; H01L 21/02192 20130101; H01L 21/31604
20130101; H01L 21/02211 20130101; H01L 21/02164 20130101; H01L
21/02238 20130101; H01L 21/0214 20130101; H01L 21/0228 20130101;
H01L 21/3165 20130101; H01L 21/02181 20130101; H01L 21/02189
20130101; H01L 21/02183 20130101; H01L 21/02175 20130101 |
Class at
Publication: |
438/785 ;
438/786; 438/787; 438/790 |
International
Class: |
H01L 021/469; H01L
021/31 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 27, 2001 |
KR |
2001-51703 |
Claims
What is claimed are:
1. A method of forming an insulating film in a semiconductor device
comprising the steps of: providing a silicon substrate on which an
under layer is formed; and alternately performing a first process
of injecting a silicon source and a second process of injecting an
oxidization reaction gas to form an oxide film on said under layer,
wherein said oxidization reaction gas employs oxygen radical or
ozone.
2. The method of forming an insulating film in a semiconductor
device according to claim 1, wherein said silicon source is any one
of a silicon organic precursor and SiH.sub.4.
3. The method of forming an insulating film in a semiconductor
device according to claim 2, wherein said silicon organic precursor
includes alkoxide series of Si(OR).sub.4, amine series of
Si(NR.sub.2).sub.4 and alkyle series of SiR.sub.4, where R is
CH.sub.3, C.sub.2H.sub.5, C.sub.3H.sub.7 or C.sub.4H.sub.9.
4. The method of forming an insulating film in a semiconductor
device according to claim 1, wherein said oxide film is formed by
using any one of an atomic layer deposition (ALD) apparatus.
5. The method of forming an insulating film in a semiconductor
device according to claim 1, further including the step of forming
a thermal oxide film on said under layer by means of a thermal
oxidization process using oxygen radical or ozone, before said
first process is performed.
6. The method of forming an insulating film in a semiconductor
device according to claim 5, wherein said steps of forming said
thermal oxide film and said oxide film are performed in-situ
method.
7. A method of forming an insulating film in a semiconductor device
comprising the step of forming a silicon oxynitride film using a
silicon organic precursor, an oxygen precursor and a nitrogen
precursor, wherein said oxygen precursor employs an oxygen radical,
and said nitrogen precursor employs one of a nitrogen radical,
ammonium and N.sub.2O.
8. The method of forming an insulating film in a semiconductor
device according to claim 7, wherein said silicon organic precursor
includes alkyle series of SiR.sub.4, where R is CH.sub.3,
C.sub.2H.sub.5, NCH.sub.3 or OC.sub.2H.sub.5.
9. The method of forming an insulating film in a semiconductor
device according to claim 7, wherein said silicon oxynitride film
is formed by sequentially performing the silicon organic precursor
injection process, the oxygen radical injection process and the
nitrogen radical injection process.
10. The method of forming an insulating film in a semiconductor
device according to claim 7, wherein said silicon oxynitride film
is formed by sequentially performing the silicon organic precursor
injection process, the ammonium injection process and the oxygen
radical injection process.
11. The method of forming an insulating film in a semiconductor
device according to claim 7, wherein said silicon oxynitride film
is formed by sequentially performing the silicon organic precursor
injection process, the N.sub.2O injection process and the oxygen
radical injection process.
12. A method of forming an insulating film in a semiconductor
device comprising the step of alternately performing a metal
precursor injection process and an oxidization reaction gas
injection process to form a metal oxide film on a silicon
substrate, wherein said oxidization reaction gas employs oxygen
radical or ozone.
13. The method of forming an insulating film in a semiconductor
device according to claim 12, farther including the step of
performing a rapid thermal process under oxygen radical atmosphere
after said metal oxide film is formed.
14. The method of forming an insulating film in a semiconductor
device according to claim 12, wherein the further including the
step of performing the silicon precursor injection process before
the metal precursor injection process.
15. The method of forming an insulating film in a semiconductor
device according to claim 14, wherein in said silicon precursor
injection process and said metal precursor injection process, the
composition of silicon and metal is controlled by the process
time.
16. The method of forming an insulating film in a semiconductor
device according to claim 15, wherein said silicon precursor
injection process and said metal precursor injection process are
repeatedly performed, and wherein the composition of silicon and
metal is adjusted by gradually reducing the time to inject the
silicon precursor and gradually increasing the time to inject the
metal precursor.
17. The method of forming an insulating film in a semiconductor
device according to claim 12, wherein said metal precursor
injection process is performed in two steps where different metal
precursors are used in each step.
18. The method of forming an insulating film in a semiconductor
device according to claim 12, wherein said metal precursor
injection process is performed in two steps, where different metal
precursors are used in each step, and wherein after each step, the
oxidization reaction gas injection process is performed to form
different types of metal oxide films in a multi-layer
structure.
19. A method of forming an insulating film in a semiconductor
device comprising the steps of: alternately performing a metal
precursor injection process and a hydrogen radical injection
process; and performing an annealing process under oxygen radical
or ozone atmosphere to form a metal thermal oxide film.
20. A method of forming an insulating film in a semiconductor
device comprising the step of: alternately performing a metal
precursor injection process, an oxygen radical injection process, a
dopant precursor injection process and a hydrogen radical injection
process to form a metal oxide film.
21. The method of forming an insulating film in a semiconductor
device according to claim 12, 19 or 20, wherein said metal
precursor includes alkoxide series of M(OR).sub.x, amine series of
M(NR.sub.2).sub.x and alkyle series of MR.sub.x, where R is
CH.sub.3, C.sub.2H.sub.5, C.sub.3H.sub.7 or C.sub.4H.sub.9.
22. The method of forming an insulating film in a semiconductor
device according to claim 12 or 20, wherein said metal oxide film
is any one of oxides of lanthanum group metals such as TiO.sub.2,
Ta.sub.2O.sub.5, Al.sub.2O.sub.3, ZrO.sub.2, HfO.sub.2,
Y.sub.2O.sub.3 and La.sub.2O.sub.3, Gd.sub.2O.sub.3 and
Pr.sub.2O.sub.3 to which said dopant precursor is injected.
23. The method of forming an insulating film in a semiconductor
device according to claim 19, wherein said metal thermal oxide film
is any one of oxides of lanthanum group metals such as TiO.sub.2,
Ta.sub.2O.sub.5, Al.sub.2O.sub.3, ZrO.sub.2, HfO.sub.2,
Y.sub.2O.sub.3 and La.sub.2O.sub.3, Gd.sub.2O.sub.3 and
Pr.sub.2O.sub.3 to which said dopant precursor is injected.
24. The method of forming an insulating film in a semiconductor
device according to claim 19, wherein said silicon oxynitride film
is formed by an atomic layer deposition (ALD) method.
25. The method of forming an insulating film in a semiconductor
device according to claim 12 or 20, wherein said metal oxide film
is formed by an atomic layer deposition (ALD) method.
26. The method of forming an insulating film in a semiconductor
device according to claim 19, wherein said metal thermal oxide film
is formed by an atomic layer deposition (ALD) method.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates generally to a method of
forming an insulating film in a semiconductor device. More
particularly, the present invention relates to a method of forming
an insulating film in a semiconductor device capable of improving
an interface characteristic and controlling the composition ratio
using an atomic layer deposition method or a chemical vapor
deposition method.
[0003] 2. Description of the Prior Art
[0004] Recently, the manufacture technology of semiconductor
devices has been remarkably improved. In particular, as high
performance microprocessor and wireless communication markets are
expanded, the manufacture technology of CMOS devices becomes
further important.
[0005] In the process of manufacturing a MOS transistor made of a
metal, oxide and silicon (Si), a gate dielectric film is mostly
formed of oxide or oxynitride. The operating characteristic of the
device depends on the characteristic of the gate dielectric film.
In other words, if the interface characteristic and the film
quality of the gate dielectric film are improved, the operating
characteristic of the device can be improved. Therefore, there is a
need for an improvement of a process technology for forming an
oxide film and an oxynitride film.
[0006] The oxide film is used to manufacture not only a CMOS device
but also a memory device. The oxide film used for the dielectric
film of the memory device must have a different characteristic from
the oxide film used for the gate dielectric film of the CMOS
device.
[0007] The oxide film used for the gate dielectric film must have a
good adaptability with silicon (Si) being an underlying layer and
have a good interface stability with silicon (Si). On the other
hand, the oxide film used as the dielectric film in the memory
device has good characteristics such as a leakage current, a
dielectric constant, etc. but the interface characteristic of the
oxide film with an underlying electrode are less considered.
Therefore, there is a need for an oxide deposition system that can
be further easily applied variations in the process parameter and
selection of the material.
[0008] Generally, the gate oxide film is mainly formed of amorphous
silicon oxide that is thermally grown. This thermal oxide film has
a good interface characteristic, less leakage current and a low
density of defective charges. It is usually required that the gate
oxide film have the defective charge density of about
10.sup.10/cm.sup.2eV.
[0009] As the semiconductor devices are higher integrated, there is
a trend that the equivalent thickness of the oxide film is reduced
from 20 .ANG. to below 10 .ANG..
[0010] According to a theoretical research by Tang, et al., the
minimum equivalent thickness of oxide at which the oxide can
maintain the bulk characteristic is 7 .ANG.. If the equivalent
thickness is below it, the oxide does not function as an insulator
by shortage. However, though the equivalent thickness of the oxide
film is thick, there is a limit that the equivalent thickness of
the oxide film is reduced since the tunneling current is increased
in equivalent thickness of below 20 .ANG..
[0011] In order to solve these problems, there was proposed a
method of growing oxynitride instead of oxide to reduce the
tunneling current effect even in a thin thickness so that the
leakage current characteristic can be improved. It was reported
that the dielectric constant (.kappa.) of pure silicon nitride
(Si.sub.3N.sub.4) is about 7 and oxynitride prevents penetration of
boron(B) (see Y. Wu et al., IEEE Electron Device Letter, 19, p
367).
[0012] However, it was reported that it would be very effective to
add a little amount of nitrogen (N) but if a large quantity of
nitrogen (N) is added, the characteristic of the device is degraded
due to excessive charges by 5 valence nitrogen atoms and defects in
the interface.
[0013] In view of the above, there is a need for a technology of
adding a little nitrogen (N) and easily controlling the composition
of nitrogen (K. A. Ellis et al., Applied Physics Letter, 74, p
967).
[0014] In order to deposit oxide having more a greater dielectric
constant, control of a fine composition is required. However, as
there is a limit that oxynitride reduce the equivalent thickness of
silicon oxide, there has been a research into a metal oxide having
a great dielectric constant as a substitution oxide.
[0015] There was a research to oxidize Ta, Ti, etc. to produce a
metal oxide. If this metal oxide is used, however, the
characteristic of the device is degraded as a silicon oxide is
generated due to the interface reaction with silicon. Therefore,
there is a need for development of a metal oxide that is
thermodynamically stable.
[0016] According to recent prior arts, it was reported that the
crystallization temperature can be increased, the amorphous state
can be maintained and generation of SiO.sub.2 can be mitigated by
growing oxide such as Ta.sub.1-xAlO.sub.y or
Ta.sub.1-xSi.sub.xO.sub.y TaO.sub.x in which a small amount of
silicon (Si) or aluminum (Al) is added, so that a good
characteristic and the surface shape could be obtained (Glen B.
Alers et al., U.S. Pat. No. 6,060,406A). In order to control of
such fine composition, it is considered that an atomic layer
deposition (ALD) is most suitable.
[0017] In case of aluminum (Al), it was reported that the stability
is maintained but the dielectric constant is not so high, so that
boron (B) can be diffused in a subsequent process. In addition, as
deposition of aluminum is performed in a thermodynamically unstable
state, silicate can be generated to degrade the characteristic of
the device. However, if a thin film is grown with the atomic layer
being controlled, a thin film that is thermally stable can be grown
and generation of silicate can be also prevented. Actually, there
was a report that generation of silicate is prohibited in case of
the atomic layer chemical deposition method. Therefore, if the ALD
method is used, the stability of the interface can be
maintained.
[0018] For the purpose of the interface stability of oxides used
for this gate oxide film, there has recently been a study on oxide
of lanthanum group atoms such as Hf, Zr, Y, La, Pr, Nd, Dy, Gd,
etc. There was reported that general characteristics having an
interface characteristic with silicon are good. In case of Zr,
ZrO.sub.2, ZrSiO.sub.4, etc. maintains with a stable state even it
contacts silicon. It was reported that the specific inductive
capacity of ZrO.sub.2 is 25 but the specific inductive capacity of
ZrSiO.sub.4 is 12.6. However, ZrO.sub.2 is crystallized and becomes
ion-conductive at low temperature. The channel mobility of
electrons is reduced due to a hetero interface with silicon. In
case of ZrSiO.sub.4, though the crystallization temperature is
high, there is a disadvantage that a deposition material of
ZrO.sub.2 can be generated.
[0019] According to a recent article, in case that silicon oxide is
grown by adding a small amount of Zr of 3-5% in the shape of
ZrSi.sub.xO.sub.y, a good oxide film having a low leakage current
and having an amorphous state can be obtained (G. D. Wilk et al.,
Journal of Applied Physics, 87, p 484).
[0020] A similar result was obtained from HfSi.sub.xO.sub.y as well
as ZrSi.sub.xO.sub.y. However, this silicon (Si)-rich metal oxide
is deposited by means of a sputtering method. This method has
disadvantages that it is difficult to control the composition of
silicon and metal, and must use a target the composition of which
is first set. Therefore, if the ALD method is employed, it would be
helpful to find an optimum composition having a good characteristic
since the change of the composition can be easily controlled. Also,
in case of amorphous, Gd.sub.2O.sub.3, Y.sub.2O.sub.3, etc. have a
low leakage current and prohibit an interface reaction with
silicon. Also, Gd.sub.2O.sub.3, Y.sub.2O.sub.3, etc. have a good
uniformity of a thin film and a flat surface shape can be obtained
from them. If Gd.sub.2O.sub.3, Y.sub.2O.sub.3, etc. are grown in a
crystal shape, they have a higher leakage current than amorphous
and its surface shape is bad. Also, it was reported that the
heating rate is high and a SiO.sub.2 layer can be formed under
oxygen atmosphere at high temperature. Therefore, it is preferred
that a subsequent process is performed under an inactive gas
atmosphere and Gd.sub.2O.sub.3, Y.sub.2O.sub.3, etc. is maintained
in an amorphous shape.
[0021] In addition, it was reported that though the oxides of a
lanthanum series have a good interface stability but the flat
voltage is moved by about -1.4V since positive charges exist within
a thin film.
[0022] There was a report that in a prior art the characteristic of
oxide is improved by adding the dopant, the characteristic can be
improved by reducing defects in the interface such as an unwanted
strained bond by doping IV-group materials into III-group and
VB-group oxides. It is preferred that the doping concentration can
be controlled from 0.1% to 10%. It would be advantageous that the
composition is controlled using the ALD method (W. H. Lee et al.,
U.S. Pat. No. 923,056A).
[0023] As such, in order to grow an optimum oxide having a good
characteristic while having the interface stability with silicon,
Si.sub.xM.sub.1-xO.sub.y oxide in which silicon and metal are mixed
and M.sub.1xM.sub.2(1-x)O.sub.y oxide in which metal (M.sub.1) and
metal (M.sub.2) are mixed are usually employed. As there is a
report that the crystallization temperature can be increased or the
interface can be improved by adding silicon and 4-group elements,
there is a need for a new deposition method by which the
composition can be finely controlled.
SUMMARY OF THE INVENTION
[0024] It is therefore an object of the present invention to
provide a method of forming an insulating film in a semiconductor
device capable of solving the above problems by controlling the
pulse construction and the supply time of source and radicals in
the deposition process using an atomic layer deposition (ALD)
method.
[0025] Another object of the present invention is to provide a
method of growing an oxide film for a gate or a dielectric film in
a memory device by variously controlling the composition, the
doping concentration and the thickness of a thin film in a silicon
oxide, silicon oxynitride, a metal oxide having a high dielectric
constant or oxides made of these compounds and a doping oxide using
the ALD method.
[0026] In order to accomplish the above object, a method of forming
an insulating film in a semiconductor device according to the
present invention is characterized in that it comprises the step of
alternately performing a silicon source injection process and an
oxidization reaction gas injection process to form a deposition
oxide film on a silicon substrate, wherein the oxidization reaction
gas employs oxygen radical or ozone.
[0027] A method of forming an insulating film in a semiconductor
device according to the present invention is characterized in that
it comprises the step of forming a silicon oxynitride film using a
silicon organic precursor, an oxygen precursor and a nitrogen
precursor, wherein the oxygen precursor employs an oxygen radical,
and the nitrogen precursor employs one of a nitrogen radical,
ammonium and N.sub.2O.
[0028] A method of forming an insulating film in a semiconductor
device according to the present invention is characterized in that
it comprises the step of alternately performing a metal precursor
injection process and a hydrogen radical injection process and then
performing an annealing process under oxygen radical or ozone
atmosphere to form a metal thermal oxide film.
[0029] A method of forming an insulating film in a semiconductor
device according to the present invention is characterized in that
it comprises the step of alternately performing a metal precursor
injection process, an oxygen radical injection process, a dopant
precursor injection process and a hydrogen radical injection
process to form a metal oxide film.
[0030] A silicon thermal oxide film has been used the oxide film
for a gate so far, which is grown at a high temperature of over
800.degree. C. In case of manufacturing a high speed MOSFET device
the channel of which is made of SiGe, however, as the temperature
in a subsequent process must be lower to below 800.degree. C., it
is required that the oxide film be grown at low temperature. In
order to implement it, a thermal oxide film is formed at low
temperature using ozone or oxygen radicals or SiO.sub.2 is
deposited using a silicon (Si) precursor and a reaction gas.
[0031] Generally speaking, the interface characteristic of the
deposition material is less than the thermal oxide film but is
rapid in the deposition speed. Therefore, the thermal oxide film is
formed at the interface with the silicon substrate using these
advantages and a deposition oxide film is formed thereon to
implement a thin SiO.sub.2 film. In this case, the ALD method may
be employed.
[0032] Also, the leakage current can be reduced and the penetration
of boron (B) can be prohibited, by adding nitrogen (N) to form a
thin film of a Si-O-N shape. As a result, the characteristic
improvement effect can be obtained by adding nitrogen (N) during
the ALD process.
[0033] As the channel length is reduced depending on higher
integrated devices, if an oxide film such as SiO.sub.2 or SiON is
employed, the leakage current can be increased. Therefore, it is
required that a metal oxide of a high dielectric constant be
instead used.
[0034] Materials that will be used as a next-generation oxide film
for a gate include Ti, Ta, etc. A study on these oxides has been
made. There was a report that SiO.sub.2 is generated at the
interface to reduce the capacitance if these oxides are employed.
However, it was also reported that if silicon (Si) and aluminum
(Al) are added, the crystallization temperature is increased and
generation of SiO.sub.2 is delayed.
[0035] For the purpose of the interface stability with silicon
(Si), a study has been made on metal oxides of Y, Zr, Hf and
lanthanum groups. It was reported that the characteristic can be
improved by doping 4-group metal and silicon (Si) to 3-group and 5
group oxides.
[0036] Further, as oxides of Zr or Hf itself have a low
crystallization temperature, there was a report that it would be
effective to add silicon (Si) in a Si.sub.xZr.sub.1-xO.sub.y or
Si.sub.xHf.sub.1-xO.sub.y shape in order to maintain it in an
amorphous shape.
[0037] Therefore, in the prevent invention, oxides are deposited by
means of an atomic layer deposition method using organic source and
oxygen radicals to effectively control the composition and the
doping concentration.
BRIEF DESCRIPTION OF THE DRAWINGS
[0038] The aforementioned aspects and other features of the present
invention will be explained in the following description, taken in
conjunction with the accompanying drawings, wherein:
[0039] FIG. 1a is a cross-sectional view of a semiconductor device
for explaining a method of forming an oxide film made of a thermal
oxide film and a deposition oxide film;
[0040] FIG. 1b is a process flow for explaining FIG. 1a;
[0041] FIGS. 2a through 2d are process flows for explaining a
method of forming a silicon oxynitride film according to one
embodiment of the present invention;
[0042] FIG. 3a, FIG. 3b and FIG. 3e are process flows for
explaining a method of forming a metal oxide film having a high
dielectric constant according to one embodiment of the present
invention;
[0043] FIG. 3c is a cross-sectional view of the device for
explaining FIG. 3e;
[0044] FIG. 3d is a graph for explaining FIG. 3e;
[0045] FIG. 4a and FIG. 4b are cross-sectional views of the device
for explaining a method of forming a metal thermal oxide film
according to another embodiment of the present invention;
[0046] FIG. 4c is a process flow for explaining FIG. 4a and FIG.
4b;
[0047] FIG. 5a and FIG. 5c are cross-sectional views for explaining
a method of forming a metal oxide film made of an oxidized mixture
of a metal (M.sub.1) and another metal (M.sub.2);
[0048] FIG. 5b and FIG. 5d are process flows for explaining FIG. 5a
and FIG. 5c;
[0049] FIG. 6 is a process flow for explaining a metal oxide film
for which doping is performed; and
[0050] FIG. 7 is a construction of a deposition apparatus used to
deposit oxide on a semiconductor substrate using an atomic layer
deposition method.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0051] The present invention will be described in detail by way of
a preferred embodiment with reference to accompanying drawings, in
which like reference numerals are used to identify the same or
similar parts.
[0052] FIG. 1a is a cross-sectional view of a semiconductor device
for explaining a method of forming an oxide film made of a thermal
oxide film and a deposition oxide film, and FIG. 1b is a process
flow for explaining FIG. 1a.
[0053] Referring now to FIG. 1a, a thermal oxide film 2 is grown on
a silicon substrate 1. Then, a deposition oxide film 3 is formed on
the thermal oxide film 2. First, the thermal oxide film 2 of a
given thickness is grown on the surface of the silicon substrate 1
by supplying oxygen radicals or ozone into the chamber of a given
temperature (T.sub.1).
[0054] In case that the thermal oxide film is grown using ozone or
oxygen radical, the growth temperature is lower than the case of
using oxygen molecules. However, the thermal oxide film is
generally grown at the temperature of more than 500.degree. C. If
the growth temperature of oxide is low, the temperature of the
substrate is lowered. For this temperature control, a rapid thermal
process (RTP) is employed so that the temperature of the substrate
can be controlled by means of a radiant heat of a lamp.
[0055] After the temperature (T.sub.2) inside the chamber is
lowered, a purge process is performed if the temperature is
stabilized. Thereafter, after silicon organic source or SiH.sub.4
is supplied into the chamber, a purge process is performed. A
reaction gas is supplied into the chamber to form the silicon
deposition oxide film 3 on the thermal oxide film 2.
[0056] As above, a deposition process of one cycle that consists of
a silicon precursor injection step, a first purge step, an ozone or
oxygen injection step and a second purge step is repeatedly
performed to form an oxide film of a given thickness.
[0057] The silicon organic source used as the silicon (Si)
precursor may include Si(OC.sub.2H.sub.5).sub.4 (TEOS),
Si(N(CH.sub.3).sub.2).sub.4 (TDMAS),
Si(N(C.sub.2H.sub.5).sub.2).sub.4, Si(CH.sub.3).sub.4,
Si(C.sub.2H.sub.5).sub.4, etc. Oxygen radical (O*) dissolved by
plasma, ozone (O.sub.3) obtained using ultraviolet, etc. are used
as a reaction gas. As this oxygen radical or ozone has a good
reactivity, it helps an oxide film having a good characteristic to
be grown at low temperature.
[0058] In case of growing an oxide film having a good stack density
using a chemical vapor deposition (CVD) method, TEOS or TDMAS is
generally used as a source. In this case, the oxide film
(SiO.sub.2) is deposited at the rate of several .ANG. per minutes
at the temperature of 300-500.degree. C. However, the present
invention employs an atomic layer deposition equipment. Thus, the
amount of oxide deposited in one cycle is self-limited but the
thickness of 10-30 .ANG. per minutes can be deposited due to a high
deposition speed. This deposition speed has a close relation with
the size of the chamber. In order to grow the thermal oxide film of
70 .ANG., about 30 minutes of time is required. Thus, there is a
significant difference in the growth rate.
[0059] That is, the thermal oxide film has better interface
characteristic and film quality than the deposition oxide film but
is slower in the growth speed than the deposition oxide film.
Therefore, the present invention grows the thermal oxide film 2 at
the interface of the silicon substrate 1 and then forms the
deposition oxide film 3 on the thermal oxide film 2 in-situ to
obtain an oxide film having good interface and deposition speed
characteristics.
[0060] FIGS. 2a through 2d are process flows for explaining a
method of forming a silicon oxynitride film according to one
embodiment of the present invention.
[0061] Referring now to FIG. 2a, there is shown a process of
depositing a silicon oxynitride film that consists of a silicon
precursor injection step, a first purge step, an oxygen radical
injection step, a second purge step and a nitrogen radical
injection step. The injection time of oxygen radical and nitrogen
radical is controlled to adjust the composition ratio of oxygen and
nitrogen.
[0062] FIG. 2b shows a process of forming a silicon oxynitride
(Si-O-N) film that consists of a SiR.sub.4 (R is legand, i.e.,
CH.sub.3, C.sub.2H.sub.5, NCH.sub.3, OC.sub.2H.sub.5, etc.)
injection step, a purge step, an ammonium injection step and an
oxygen radical injection step.
[0063] FIG. 2c is a process of forming a silicon nitride film that
consists of a silicon precursor injection step, a first purge step,
a N.sub.2O injection step and a second purge step. In this case, it
is difficult to independently control the composition ratio of
oxygen and nitrogen. Therefore, as shown in FIG. 2d, the first
purge step is performed after a silicon precursor is injected and
the second purge is performed after N.sub.2O is injected. In
addition, after oxygen radical is injected, a third purge step is
performed to form a silicon nitride film.
[0064] As above, the composition of nitrogen and oxygen can be
independently controlled by additionally using oxygen radical.
[0065] Meanwhile, as the process in FIG. 2c using only the silicon
precursor and N.sub.2O as a reaction gas can reduce the number of
the process step, it is advantageous to apply the process of FIG.
2c in view of the productivity if a desired composition is possible
by some degree.
[0066] FIGS. 3a through 3d are process flows for explaining a
method of forming a metal oxide film having a high dielectric
constant according to one embodiment of the present invention.
[0067] Metals having a high dielectric constant include elements of
Ta, Ti, Al, Y, Zr, Hf and a lanthanum group. The metal precursor
may include alkoxide series of M(OR).sub.x, amine series of
M(NR.sub.2).sub.x and alkyle series of MR.sub.x (R is an alkyl
radical such as CH.sub.3, C.sub.2H.sub.5, C.sub.3H.sub.7,
C.sub.4H.sub.9, etc.) as an organic substance. The reaction gas may
include oxygen radical or ozone. In the existing atomic layer
deposition (ALD) method, the metal oxide is deposited using a
MCl.sub.x precursor and H.sub.2O as a reaction gas. In the present
invention, however, oxide is deposited using reaction of an organic
substance precursor with oxygen radical. If the oxide is deposited
using an organic substance at low temperature, a porous film having
a low density can be formed and an impurity such as carbon may
remain. Specially, if this deposited oxide is used as a gate oxide
film, degradation of oxygen is caused. Therefore, if the thin film
is grown and the thin film is then maintained at an oxygen radical
atmosphere with increased temperature, the content of carbon is
significantly lowered and the density of the thin film is
increased. Thus, as shown in FIG. 3a, a deposition process
consisting of a metal precursor injection step, a first purge step,
an oxygen radical injection step and a second purge step at a low
temperature (T.sub.2) is performed. Then, an annealing process is
performed under oxygen or oxygen radical atmosphere at a high
temperature with the temperature (T.sub.1) raised.
[0068] Recently, it was reported that silicate of
Si.sub.xHf.sub.1-xO.sub.- y, Si.sub.xZr.sub.1-xO.sub.y, etc. in
which a metal oxide of a high dielectric constant such as Hf or Zr
is added to silicon is maintained at an amorphous state even at a
high temperature. There is shown a process of adding silicon to
form the metal oxide in FIG. 3b.
[0069] FIG. 3b shows a process of forming the metal oxide that
consists of a silicon precursor injection step, a first purge step,
a metal (M) precursor injection step, a second purge step, an
oxygen radical injection step and a third purge step. At this time,
it is very important to control the composition ratio of silicon
and metal (M). The composition ratio of metal and silicon could be
controlled by adjusting the injection time of silicon and metal. If
the composition of silicon and metal is uniform, a constant process
time can be maintained as the process period is repeated.
[0070] If the amount of silicon is increased, the dielectric
constant is usually lowered but the crystallization temperature is
increased. Therefore, if the composition within the interface and
the thin film is controlled, a further optimum condition can be
easily obtained. It would be thus effective to control the growth
of the thin film by means of the ALD method than chemical vapor
deposition method.
[0071] For example, as shown in FIG. 3e, if the injection time of
silicon is reduced, the injection time of metal is increased as the
process is proceeded, the content of silicon within the metal oxide
12 is reduced as it is far from the interface with the silicon
substrate 11, as shown in the graph of FIG. 3d.
[0072] FIG. 3c shows the metal oxide 12 formed on the silicon
substrate 11, which shows that the content of silicon within the
metal oxide 12 is reduced as it is far from the interface with the
silicon substrate 11.
[0073] FIG. 4a and FIG. 4b are cross-sectional views of the device
for explaining a method of forming a metal thermal oxide film
according to another embodiment of the present invention, and FIG.
4c is a process flow for explaining FIG. 4a and FIG. 4b.
[0074] FIG. 4a is a cross-sectional view of the metal thermal oxide
film in which a metal 22 is deposited on a silicon substrate 21
using a metal organic source and FIG. 4b is a cross-sectional view
of the metal thermal oxide film in which the metal 22 is oxidized
using a hydrogen radical as a reaction gas to form a metal oxide
film 23.
[0075] As shown in FIG. 4c, after a metal is deposited at a low
temperature (T.sub.2), as shown in FIG. 4a, the temperature is
raised so that the metal can be exposed to oxygen radical of a high
temperature (T.sub.1), thus forming the metal oxide film 23.
[0076] As shown in FIG. 4c, a process consisting of a metal
injection step, a first purge step, a hydrogen radical injection
step and a second purge step, at a low temperature (T.sub.2), are
repeatedly performed to deposit a metal of a desired thickness.
Then, the temperature is raised so that the metal can be exposed to
the oxygen radical, thus forming the metal oxide film 23.
[0077] The metal thermal oxide film formed thus has a good and
stable film quality. These processes are possible in a metal on
which the thermal oxide film can be formed.
[0078] FIGS. 5a and FIG. 5c are cross-sectional views for
explaining a method of forming a metal oxide film made of an
oxidized mixture of a metal (M.sub.1) and another metal (M.sub.2),
and FIG. 5b and FIG. 5d are process flows for explaining FIG. 5a
and FIG. 5c.
[0079] FIG. 5a is a cross-sectional view of the metal oxide film 32
formed on a silicon substrate 31, which is made of an oxidized
metal compound. As shown in FIG. 5b, a first metal (M.sub.1)
precursor injection step, a first purge step, a second metal
(M.sub.2) precursor injection step and a second purge step are
sequentially performed to form the metal oxide film 32 on the
silicon substrate 31.
[0080] Referring to FIG. 5c, the first metal oxide film 33 made of
the metal (M.sub.1) and the second metal oxide film 34 made of the
metal (M.sub.2) are alternately stacked on the silicon substrate
31. As shown in FIG. 5d, a first metal (M.sub.1) precursor
injection step, a first purge step, an oxygen radical injection
step, a second purge step, a second metal (M.sub.2) precursor
injection step and a third purge step are sequentially performed to
alternately stack the first metal oxide film 33 and the second
metal oxide film 34 on the silicon substrate 31.
[0081] In other words, FIG. 5a and FIG. 5b present a technology of
oxidizing two metal compounds at once to form a metal oxide film
while FIG. 5c and FIG. 5d present a technology of alternately
stacking and oxidizing different two metal oxides to form a metal
oxide film.
[0082] As above, the shape of oxide can be varied depending on the
supply time of the precursor and radical. Generally, the leakage
current characteristic is degraded as the gate oxide film has a lot
of interfaces. It is advantageous that an oxide film of a compound
shape is used rather than a structure in which oxides are stacked
in view of the characteristic of the device.
[0083] FIG. 6 is a process flow for explaining a metal oxide film
for which doping is performed. The process consists of a metal
precursor injection step, a first purge step, an oxygen radical
injection step, a second purge step, a dopant precursor injection
step, a third purge step, a hydrogen radical injection step and a
fourth purge step.
[0084] In case of forming a metal oxide film having a good
interface characteristic by doping 4-group materials to 3-group or
5-group metal oxides or forming an oxide film by adding silicon or
aluminum to TaO.sub.x, a dopant precursor is used in order to
improve the characteristic, as above. At this time, the dopant
reduces the hydrogen radical.
[0085] FIG. 7 is a construction of a deposition apparatus used to
deposit oxide on a semiconductor substrate using an atomic layer
deposition method.
[0086] The deposition equipment used in the present invention
cannot only independently control the supply of gas but also can be
applied both to the ALD method or the CVD method.
[0087] An organic source can be stored at a container 42 and the
organic source vaporized depending on the operation of the metering
valve 41 is supplied into the chamber 60 for controlling the flow
amount of vapor, as it usually exists in an liquid state. Though
there are shown two liquid organic source containers in FIG. 7, the
number of the liquid organic source containers is not limited two.
A number of containers can be used for containing a lot of
source.
[0088] Carrier gases for carrying the liquid source of a vapor
state may include argon (Ar), etc. This carrier gas is stored at a
gas container 54 and is supplied into the chamber 60 depending on
the operation of the open and shut valve 55 and the mass flow
controller 40. Hydrogen (H) used as a reaction gas is stored at the
gas container 51 and is supplied into the plasma generator 43
depending on the operation of the open and shut valve 55 and the
mass flow controller 40. Also, the hydrogen (H) is dissolved by
plasma in a hydrogen radical state and is then supplied into the
chamber 60. Oxygen (O) used as the reaction gas is stored at the
gas container 52 and is supplied into the plasma generator 44 or an
ultraviolet generator (not shown) depending on the operation of the
open and shut valve 55 and the mass flow controller 40. Also,
oxygen (O) is dissolved by plasma in an oxygen radical state and is
then supplied into the chamber 60 where it causes an oxidization
reaction. Nitrogen (N) is stored at the gas container 534 and is
supplied into the plasma generator 45 depending on the operation of
the open and shut valve 55 and the mass flow controller 40. Also,
nitrogen (N) is dissolved in a radical state by plasma and is then
supplied into the chamber 60. A wafer 47 is located at the rear of
the chamber 60 and a plurality of lamps 46 for rapid thermal
process are installed around the wafer 47.
[0089] Also, a turbo molecule pump 49 for making an internal
atmosphere in an ultra high vacuum state is connected to the
chamber 60 via the gate valve 48. The turbo molecule pump 49 is
connected to the boost pump 61 and the dry pump 62 through the
shield valve 59.
[0090] Meanwhile, the tube passages, to which the organic source
and individual gases are supplied, are connected to the boost pump
61 and the dry pump 62 through the valves.
[0091] As can be understood from the above description, according
to the present invention, a thermal oxidization process and a
deposition process are sequentially performed to form an oxide film
having good interface characteristic and deposition speed. Also, an
oxide film, an oxynitride film and a metal oxide film are deposited
using an atomic layer deposition (ALD) method, by controlling the
pulse construction and the supply time of source and radical in
order for them to have a good interface characteristic. Therefore,
the present invention has outstanding effects that it can easily
control the content, the composition ratio and doping concentration
of a material and can obtain an oxide film having good leakage
current and interface characteristics.
[0092] The present invention has been described with reference to a
particular embodiment in connection with a particular application.
Those having ordinary skill in the art and access to the teachings
of the present invention will recognize additional modifications
and applications within the scope thereof.
[0093] It is therefore intended by the appended claims to cover any
and all such applications, modifications, and embodiments within
the scope of the present invention.
* * * * *